Abstract: The optical member of the present invention is an optical member comprising a fluoride crystal; and having an optical axis forming an angle of 10° to 36° with a <111> axis of the fluoride crystal, and a birefringence of 2.0 nm/cm or less in the optical axis direction. The optical member of the present invention can improve the yield and processing accuracy in the process of making the optical member, and can achieve sufficiently high optical characteristics.

Abstract: A soft X-ray projection exposure apparatus has at least one metal mirror in either an illumination optical system or a projection optical system. The mirror includes a metal substrate and a thin film of an amorphous substance formed thereon. The surface of the amorphous substance is polished to optical smoothness. On the surface of the thin film is a multi-layer film that reflects X-rays of a specified wavelength. The metal substrate efficiently dissipates heat to the back surface of the mirror where it can be easily cooled. The mirror has a small shape error and surface roughness, and sufficiently suppresses thermal deformation caused by irradiating electromagnetic radiation such as X-rays or light. In this manner, the soft X-ray projection exposure apparatus achieves a higher through-put of wafers.